Thank you for the answer. So I believe I can go to prior years and determine each year's interest expense that exceeded investment income (generally just interest income and maybe some non-qualified dividends). This should provide the carryover for 2019. Then in 2019, allocate as investment income much of a large 2019 capital gain and take the carryover and 2019 interest expenses as a deduction.  

How do I determine whether or not I had investment interest carryover from prior year. I am using turbo tax for the first time. My previous accountant did my taxes. Part I line 1 is blank, however, there are dollar amount entries in other areas of the 2019 form 4952.

 

I was also given a form 4952 (Alternate Minimum Tax) form. Part I is blank, there are entries in other areas of this form.

 

Can anyone advise me please?

you must amend prior years starting with the earliest.

your interest expense can then be carried forward to the next year until it is used up.

your interest expense generally is only good for offsetting dividends, so amending might not help.

There are other arcane rules. See the IRS Pubs.

you can go back three years to get a refund.